Fair Value of Horizen - Summary of changes in quantity of Horizon and respective fair value (Detail) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Jun. 30, 2022 USD ($) Horizen	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($) Horizen	Jun. 30, 2021 USD ($) Horizen	Sep. 30, 2021 USD ($) Horizen
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment Owned, Balance			$ 43,940
Net change in unrealized appreciation on investment in ZEN	$ (22,270)	$ 8,044	(35,842)	$ 33,856
Net realized gain on investment in ZEN	23	$ 296	361	$ 365
Investment Owned, Balance	$ 7,859		$ 7,859		$ 43,940
Investment in Horizen
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment Owned, Balance, Contracts | Horizen			615,585.26478971	441,290.85330434	441,290.85330434
ZEN contributed | Horizen					188,580.88160629
ZEN contributed, including repayment of ZEN receivable, related party | Horizen			16,375.40469036
ZEN distributed for Sponsor's Fee, related party | Horizen			(11,707.40244546)		(14,286.47012092)
Net change in unrealized appreciation depreciation on investment in ZEN | Horizen			0		0
Net realized gain on investment in ZEN | Horizen			0		0
Investment Owned, Balance, Contracts | Horizen	620,253.26703461		620,253.26703461		615,585.26478971
Investment Owned, Balance			$ 42,801	$ 2,502	$ 2,502
ZEN contributed					4,318
ZEN contributed, including repayment of ZEN receivable, related party			1,139
ZEN distributed for Sponsor's Fee, related party			(600)		(816)
Net change in unrealized appreciation on investment in ZEN			(35,842)		36,229
Net realized gain on investment in ZEN			361		568
Investment Owned, Balance	$ 7,859		$ 7,859		$ 42,801